Is There an Alternative to DNA?
DNA and RNA are the molecular blueprints of life. They encode and pass on genetic information, known as heredity, and they can adapt over time, the process known as evolution. Without heredity and evolution, life would not exist.
Scientists wonder whether these important traits can occur only through DNA or RNA, or if other molecules might be able to perform the exact same tasks.
At the MRC Laboratory of Molecular Biology in Cambridge, England, researchers developed chemical methods to turn DNA and RNA into six alternative genetic polymers called XNAs—xenonucleic acids. The process exchanges the sugar backbone, the deoxyribose and ribose (the “d” and “r” in DNA and RNA), for other molecules. The resulting XNA double helix is more stable than the natural genetic material. One of the XNAs, a molecule called anhydrohexitol nucleic acid, or HNA, is even capable of undergoing directed evolution. So far, the artificial material uses conventional DNA as a foundation, but some scientists hope to make synthetic organisms from scratch someday, creating an evolutionary shortcut.
Artificial XNA will drive research in medicine and biotechnology while shedding light on the original molecules that created life billions of years ago. Alternative DNA can enable scientists to make new forms of life in the laboratory. Medicine may benefit since the human body has not evolved to create enzymes that break down the foreign XNA structure. Most importantly, XNA proves that two fundamental elements of life, heredity and evolution, are possible using alternative genetic material and that life is not completely reliant on RNA and DNA as previously thought. Some scientists think we may find evidence of XNA in extraterrestrial life. However, if you’re worried about researchers creating synthetic life using XNA anytime soon, don’t be. John Chaput, a molecular biologist at Arizona State University, says, “That’s possible, but much further down the road.”
Why Do We Age?
Ponce de León sought the fountain of youth. People today pin their hopes on diets, supplements, exercise, or plastic surgery. It’s a fact: Humans age, and lots of us don’t like how aging makes us look or feel. But what if we were able to slow the aging process?
Scientists call the process of aging senescence. Why we age, according to Marquette University professor Sandra Hunter, is rather simple: “Cell death…eventually leads to systems malfunctioning and whole body death.” For example, muscle fibers and nerves connected to them gradually die, leading to a loss of strength that begins at age 50 and continues steadily thereafter.
A deeper question for scientists is, why do the cells die? They’ve come up with several theories, and most likely a combination of them explains the aging process. One theory rests on oxidative damage. Normal cell processes release harmful molecules called oxygen free radicals. Substances in the body called antioxidants neutralize some of them, but a few free radicals escape unscathed and damage cells. Oxidative damage is linked to such diseases and conditions as heart disease, diabetes, and Alzheimer’s.
Other theories pin cell death on genes, which limit how often the cells can replicate. Parts of our chromosomes, called telomeres, get shorter with each cell division until they are so short the cell can’t divide anymore. Like free radicals, shortened telomeres have been linked to a number of illnesses.
Certain genes might also control the life span of an entire organism. Research on worms shows that when scientists mutate genes related to the aging process, they can extend a worm’s life to four times its normal life span. If similar genes exist in humans and can be changed the same way, people could live up to 300 years old.
For rats, cutting their calorie intake by 30 percent of what’s considered normal lengthens their life span. Scientists predict that similar extreme dieting could have the same effect on humans. And studies in humans have shown that diet and exercise can play a role in lengthening telomeres.
“Metaphysically speaking, we age because time passes without our having died,” says Marquette philosophy professor Susan Foster. “Aging, at least, seems to beat the alternative.”
When Will We Evolve Out of Our Useless Appendages?
Never. We’re probably permanently stuck with our pinky toes, tailbone, and just about all our other evolutionary holdovers. Wisdom teeth could eventually go, but significant changes like losing an appendage (teeth included) take millions and millions of years—who knows if humans will even be around that long? What’s more, most of our seemingly useless vestiges are actually helpful.
The coccyx, or tailbone, “is an attachment point of a number of muscles at the pelvis. We need it for upright locomotion. It would be catastrophic if it went away,” says Kenneth Saladin, an anatomist and physiologist at Georgia College and State University. The pinky toe helps us keep our balance and diffuses impact throughout the foot when we run.
There are only a handful of truly useless parts of our body, but these are hanging on, too. As Saladin puts it, “Since vestiges like the muscles behind our ears have very little impact on reproductive success, there’s no way to select against them.” In other words, the ability to ear-wiggle doesn’t interfere with the ability to have kids.
The silliest of all vestiges is the male nipple. “Those don’t have a function,” Stearns says, “but they won’t disappear, either.” All embryos, male and female, begin developing according to the female body plan. Only around the sixth week of gestation do the genes on males’ Y chromosomes kick in. “The developmental plan has the two nipples there, so you can’t get rid of them genetically, because that would mess up the breasts of females.” And nobody wants that.
A lab technician looks at a petri dish containing material populated with liver cells.
How Much of the Human Body Is Replaceable?
Fans of the old TV shows and saw scientists revive nearly dead human beings, bringing them back to life with high-tech body parts that gave them extraordinary capabilities. Today, replacing parts of the human body using state-of-the-art technology is moving out of the realm of science fiction and into reality.
Replacement of body parts means transplanting organs and tissues from one person to another or using artificial body parts. Organs currently transplanted are the heart, kidneys, liver, lungs, pancreas, and intestines. Tissues and cells include the corneas, cartilage, muscles, tendons, ligaments, skin, and heart valves (mechanical versions of the valves are also used).
Artificial limbs and organs can replace parts throughout the body. Doctors commonly replace knees and hips, along with finger, elbow, and shoulder joints. Cochlear implants are electronic devices that restore hearing, and researchers are currently testing a new brain implant that can help patients who lack functioning auditory nerves. Prosthetic noses, hands, arms, and legs are available; artificial legs are among the most sophisticated prosthetics today, and researchers continue to improve “bionic” hands with an almost human sense of touch. One, the bebionic3, has 14 different grip patterns, including ones that allow users to pick up a coin or write with a pen.
The science of developing artificial body parts is constantly changing. In 2014, hospitals across the United States tested a “bioartificial” liver that combines liver cells and a mechanical device that together perform liver functions outside the body while a patient’s diseased liver regenerates healthy tissue. Researchers in Japan and elsewhere are developing 3-D printers that combine stem cells and artificial materials to custom-make artificial ears. The Japanese team hopes to also create skin and bones using this method.
Scientists are also working to grow real replacement parts in the lab. Doris Taylor of the Texas Heart Institute is one of the pioneers in using stem cells to create such body parts as hearts, livers, and kidneys for transplants. Taylor says, “I absolutely see a day where you’ll walk into a manufacturing facility somewhere, and there will be jars of kidneys, jars of livers, and jars of lungs, whatever it is you need.”
Why Do Amputees Sense a “Phantom Limb”?
Phantom limb syndrome is the sensation that an amputa
ted limb is still attached to the body and functioning normally.
Amputees report feelings of warmth, coldness, tingling, itchiness, numbness, cramping or tickling in the missing limb. An estimated 80 percent of amputees report phantom pain in their amputated limb, including shooting, piercing, burning, or stabbing pain.
What is the exact cause of phantom limb syndrome? For many years, the favored theory has been that this condition is the result of “maladaptive brain plasticity.” In short, when the brain ceases to receive signals from a missing body part, input from another body part, such as the face according to some research, begins to dominate that region of the brain. This “remapping” of the brain has long been thought to cause the syndrome.
Results of a 2013 study conducted by Oxford University neuroscientist Tamar Malkin, however, reveal the opposite. Malkin discovered that victims of phantom pain have stronger rather than weaker brain representations of the missing limb, with no indication of brain remapping. MRI scans of hand amputees and two-handed subjects taken while they were performing other activities, in this case smacking their lips—a testing of the facial region—showed no significant difference in cortex activation in the hand area between the two groups. Malkin concluded that cortical representation of the lips was not taking over areas associated with the missing hand. In addition, lip-smacking movements did not cause pain among the amputees.
“These findings shed new light on the neural correlates of the conscious experience of phantom pain,” says Malkin. “We found that the hand area of the brain seems to maintain its originally assigned role, despite the loss of original inputs and outputs,” she adds. “Our results may encourage [new] rehabilitation approaches.”
Currently, treatment for phantom limb pain includes medication, biofeedback, hypnosis, and vibration therapy. Unraveling the mystery of phantom limb syndrome will enable scientists and physicians to develop better methods of treatment for its symptoms.
Can You Upload Your Brain to a Computer?
Within the next century, scientists may discover a way of making humans—or at least what goes on inside our brains—live forever.
In a hypothetical process called mind uploading, or mind transfer, all that exists in an individual’s brain—memories, personality, consciousness, perceptions—would be transferred from the physical brain to a computational device, such as a computer or an artificial neural network. Theoretically, the brain would be scanned and mapped and its activities transferred to the device, which could then run a simulation of the brain’s information-processing abilities. If the process works, the computational device would generally be able to respond in the same way as the original human brain.
In essence, mind uploading means humans could live indefinitely.
Mapping the human brain, however, is no easy task, as neuroscientists working on this technology will attest. The human brain contains roughly 85 billion neurons, each one connected to thousands of others via branches called dendrites and axons. While many people would disagree, some scientists believe who we are—our consciousness, our memories, our personalities—lies solely in the sum of the brain’s activity, the patterns of the electrochemical impulses that occur both in our waking and sleeping hours. Researchers can detect and record electrical brain activity, but they have yet to unlock the mystery of how neurons interact, among other intricate workings of the brain. Many scientists are seeking answers to these stumbling blocks, however, and some predict mind uploading will be a reality one day.
The prospect of such “eternal life” technology has elicited strong responses from opponents. Some claim that the preservation of the brain after biological death would violate their religious beliefs. Others argue that natural aging and death are part of the human experience and it would be wrong to extend life beyond what nature provides. Ethical and legal issues also need to be considered. Political and economic implications would also come into play.
The flip side, of course, is to consider the benefits to humanity of having the brain of an Einstein, a Picasso, or a Lincoln from which to extract knowledge and study. Mind uploading would enable family members to have access to the uplifting and informative memories of long-dead ancestors. In short, the technology holds the potential to enable each of us to remain connected, and contributing, to the society that helped form us.
What Is Intelligence?
The true meaning of intelligence is a difficult code to crack. Simply speaking, intelligence is the ability to acquire knowledge and skills. But which skills and how we measure them varies. Furthermore, why do some people, such as Albert Einstein, have superior intelligence?
Academics tend to measure intelligence using intelligence quotient (IQ) tests. French psychologists Alfred Binet and Theodore Simon developed the first modern intelligence test in 1904. Each year, a group of test takers establishes the average intelligence, represented by a score of 100. Since the first tests, each generation seems to have grown in intelligence, a phenomenon called the Flynn effect. When the test subjects retake older IQ tests, they almost always score better than 100. But that doesn’t necessarily mean we are more intelligent than our grandparents—we may just be better at taking tests.
Aptitude tests are one way of measuring intelligence, but scholars note that most aptitude tests are biased from the writer’s point of view. For example, Isaac Asimov, a novelist and professor of biochemistry, once wrote that he believed himself smarter than his auto-repair mechanic. But if his auto-repair mechanic had devised a test of intelligence, Asimov wrote that he would certainly have failed.
For years, many researchers associated skull size with high intelligence test scores. But in 2007, after decades of research, neuroscientists Rex Jung and Richard Haier published a study describing 37 different neuroimaging studies of IQ. The surprising results suggest that intelligence is related not to brain size or structure, but instead to how efficiently information travels through the brain. The scientists found the frontal and parietal lobes play the most important role in intelligence. These areas also control attention, memory, and language, which Jung and Haier believe is not a coincidence. However, the neuroscientists found that intelligence is scattered throughout the brain; no single region is wholly responsible. Perhaps this explains why some people have higher levels of artistic talent, mathematical skill or musical ability. Since no single structure is responsible for general intelligence, different types of brain designs may produce different types of intelligence.
Understanding the path intelligence takes throughout the brain can boost IQ. It can also help treat people who are intellectually or developmentally disabled. Dissecting how we learn can be an important aid for children in schools. But even an IQ test does not account for all types of brainpower. Einstein himself proclaimed, “The true sign of intelligence is not knowledge but imagination.”
CHAPTER 4
Earth
What Causes Volcanic Lightning?
On March 10, 2010, Eyjafjallajökull volcano, a caldera in Iceland covered by an ice cap, erupted. It sent plumes of clouds across most of Europe and the Atlantic Ocean. Photos of the eruption show lightning originating and ending in the cloud of ash that hovered over the volcanic opening.
The largest volcanic storms are similar to supercell thunderstorms that spread across the American Midwest. But while those thunderstorms are fairly well understood, volcanic lightning still remains mysterious.
The remote location of volcanoes and infrequent eruptions make volcanic lightning difficult to study. In general, lightning occurs through the separation of positively and negatively charged particles. Differences in the aerodynamics of the particles separate the positive and negative. When the difference in charge is great, electrons flow between the positive and negative regions. A lightning bolt is a natural way of correcting the charge distribution.
So what makes volcanic lightning so difficult to understand? Scientists believe ejections from the volcano into the atmosphere carry a large electrical charge, but t
hey aren’t sure if it originates in the volcano or occurs afterward. Very high-frequency radio emissions and other types of electromagnetic waves now allow scientists to observe the lightning inside the ash plume. Since 2006, scientists have used the new technology during three separate eruptions, including Eyjafjallajökull, and can distinguish two phases for volcanic lightning. The first phase, called the eruptive phase, is the intense lightning immediately after the eruption near the crater. Presumably, charged particles from the volcano are the source of this lightning that occurs near the crater. Phase two, called the plume phase, is lightning that forms inside the ash plume downwind of the crater. The origins of this lightning remain a mystery.
In the 2010 eruption of Eyjafjallajökull, plumes of smoke significantly interrupted airline traffic, resulting in billions of dollars of lost revenue. The more we understand about volcanoes, the better we get at predicting an eruption and the potential consequences. Some scientists hope that studies of the composition of gases inside a volcanic plume could tell us more about the early stages of our planet and the conditions that created the building blocks of life, making volcanic lightning a worthy pursuit. At a safe distance, of course.
Just How Old Is Dirt?
“It depends on what you mean by dirt,” says Milan Pavich, a research geologist with the U.S. Geological Survey. “The oldest sedimentary rocks are about 3.9 billion years old—they’re in Greenland—and at one time, they were dirt. That’s pretty close to the time the Earth formed.”
100 Mysteries of Science Explained Page 9
